Gas-phase reactors, such as chemical vapor deposition (CVD) reactors, including, for example atomic layer deposition (ALD) reactors, can be used for a variety of applications, including forming layers on a substrate surface. Such reactors can be used to deposit, etch, clean, and/or treat layers on a substrate to form semiconductor devices, flat panel display devices, photovoltaic devices, microelectromechanical systems (MEMS), and the like.
A typical gas-phase reactor system includes a reactor including a reaction chamber, one or more precursor gas sources fluidly coupled to the reaction chamber, one or more carrier or purge gas sources fluidly coupled to the reaction chamber, a gas distribution system to deliver gases (e.g., the precursor gas(es) and/or carrier or purge gas(es)) to a surface of a substrate, and an exhaust source fluidly coupled to the reaction chamber.
Cross-flow reactors are a type of gas-phase reactor that are particularly useful when fast throughput and/or fast purging of a reaction chamber is desired—such as for ALD deposition. In cross-flow reactors, gasses generally enter a reaction chamber at one end of the reaction chamber, flow laterally across a substrate within the reaction chamber, and exit at a second end of the reaction chamber.
Reaction chambers of cross-flow reactors are typically relatively small, allowing rapid purging of the chamber. The small reaction chamber also increases a probability that a precursor will react with the substrate surface.
However, because of the relatively small reaction chamber, cross-flow reactors tend to exhibit a pressure drop from the gas inlet side of the reaction chamber to the flow outlet side of the reaction chamber. The pressure drop can be significant in cross-flow reactors having a reaction chamber with a low vertical height and/or in reactors that have a reaction chamber with a long flow path between the gas inlet and the flow outlet. Absorption of a precursor and/or reaction of a reactant on a substrate surface is generally proportional to a pressure within the reaction chamber. Thus, the pressure drop within the reaction chamber can cause differences in adsorption/reaction rates along a surface of a substrate—e.g., between a leading and training edge of the substrate—which in turn can lead to increased non-uniformity of processes within the reaction chamber. Accordingly, improved reactors and reaction chambers are desired.
Another problem associated with cross-flow reactors is non-uniform gas flow between the reaction chamber and, for example a lower or load/unload area within the reactor. Many reactors do not form a complete seal between the reaction chamber and the load/unload area, but rather allow a controlled gas flow between the two areas. However, the pressure difference between the two areas of the reactor can differ about a perimeter of a substrate. The non-uniform pressure can, in turn, lead to backside and edge deposition on or reaction with the substrate and other problems. Accordingly, improved reactor designs with more-uniform pressure difference between the reaction chamber and another chamber within the reactor are desired.